1. Field of the Invention
The present invention relates to a main case body of a musical keyboard instrument, such as an electronic musical keyboard instrument, and more particularly to a main case body of a musical keyboard instrument that has an improved battery case and a keyboard unit.
2. Description of the Related Art
A conventional technique related to a battery case of a musical keyboard instrument has been disclosed e.g. in Japanese Utility Model Publication (Kokoku) No. H07-43943. In this conventional technique, a battery accommodating section having a box shape elongated in the key arrangement direction (key arranged direction) is formed in a lower case of a musical keyboard instrument, and a plurality of-pairs of elastic pieces are formed on the bottom of the battery accommodating section in a manner arranged in the key arrangement direction, to thereby prevent occurrence of play and rattle of batteries (cells).
A musical keyboard instrument generally has a structure in which a key supporting part that supports keys and a stopper body that limits the range of stroke of each key extend in the key arrangement direction in parallel with each other, and hence it is preferred that a battery case is formed between the key supporting part and the stopper body. In the aforementioned conventional technique as well, the battery accommodating section is formed between the key supporting part and the stopper body. In this conventional technique, however, the battery accommodating section is formed into the box shape elongated in the key arrangement direction, as mentioned above. In other words, the battery accommodating section has a structure in which a plurality of batteries are arranged lengthwise in the key arrangement direction. In this case, if a battery lid extending over the entire length of all the batteries arranged lengthwise is formed, it is easy to take in and out the batteries. However, the battery lid having a length corresponding to the entire length of all the batteries tends to be lower in mounting rigidity, and hence a slightest shock due to a fall of the lower case can cause breakage of a battery lid stopper and throw out the batteries. To avoid this problem, the battery lid is often formed to have a length corresponding to the length of one battery or one battery and a half. In this case, however, a plurality of batteries have to be inserted lengthwise from a small opening for which the lid is provided, and hence it is difficult to insert them. Further, since the batteries are arranged lengthwise, space between the electrodes of two adjacent batteries becomes so narrow that it is difficult to put a finger into the space so as to take out the batteries.
Furthermore, the most serious problem is that since the long box-shaped battery accommodating section occupies a long space at least in the key arrangement direction. Therefore, it is difficult to avoid interference between the battery accommodating section and many other parts, resulting in a very low degree of freedom in the design of the instrument. For example, when a mold for a part of the lower case-side of a keyboard unit is shared between different models of the musical keyboard instrument, it is required to change the design of the battery accommodating section (battery case) itself in a manner adapted to the shared mold.